Proper vents prevent ice dams

Why ridge, soffit openings aren't enough

By Inman News Feed
Add Comment Add Comment | Comments: 0 | Posted Jan. 7, 2011

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Why ridge, soffit openings aren't enough

Paul Bianchina
Inman News™

Q: I just read your article about preventing ice dams and have two questions. Our roof was redone three years ago and they installed a ridge vent, and I replaced all the soffit vents, but we still get icing on the back (west side) where we always had it.

1. What are your thoughts on power vents for the gable ends vs. adding more soffit vents?

2. Do we look for an insulation contractor or a roofing contractor? Our insulation in the attic is still dry, but only because I've been removing snow from the roof to eliminate the ice's fuel. I'm getting really tired of having to clear that area of the roof. Please let me know what you think. --Dave K.

A: I'm not a fan of powered anything in the way of attic vents, because I haven't seen enough evidence that the power consumed is offset by increased air flow. Beyond that, you're talking about putting vents in two different places: the gable end, which is a high, or outlet, vent; and the soffits, which is a low, or intake, vent.

For good attic ventilation, you need to have a roughly equal mix of both types of vents, so whether you need more of one or the other depends on what you already have. Also, I'm not talking about the number of vents, so much as the area of the vents. Because high vents tend to be larger in area than low vents, you typically need more low vents than you do high vents.

As far as what type of contractor, either one should be able to do the job for you, provided this person has a solid knowledge of weatherization and ventilation. Too many contractors simply throw in vents here and there without really doing the calculations as to how many are needed, and where the best placement is.

It sounds like that may have been the case with your original roofer, since just installing a ridge vent isn't enough if it doesn't provide a sufficient amount of vent area to meet the needs of your attic.

I would suggest that you contact your local utility company and ask if they have recommendations of good licensed roofing or insulation contractors who understand energy and ventilation, and go from there.

Because you have a specific problem with one side of your roof -- in your case, the back -- be sure the contractor pays particular attention to that area. There could be trees, neighboring houses or even topography issues that are affecting the airflow around your home, or you could have missing or blocked vents on that side. No matter what, the contractor may need to increase the ventilation or change its placement on that side.

Q: I have a problem that you may be able to help me with. We have a small rental house that measures 24 feet by 28 feet. It has a cement slab floor. We have a gas wall heater, which is unvented. We have a problem of excessive humidity. Some say I need more ventilation vents. I now have one 8 inches above the heater in the wall. Should I have more vents installed in the ceiling? I would very much appreciate any suggestions you think may help my problem. --Bill E.

A: Simply put, unvented gas wall heaters are dangerous. Not only is the combustion creating some of the moisture vapor problems you're dealing with, the potential for carbon monoxide poisoning is very real.

You mentioned that this is a rental property, so you have a huge liability issue here. Rather than worrying about additional vents, which would only be a Band-Aid on the problem, you instead need to replace the heater with one that's properly vented to the outside. You also need to make sure that you have a CO2 monitor installed, to give the tenants warning of the buildup of any potentially dangerous fumes in the house.

Q: Am I required to have a permit to install a pellet stove for a commercial welding shop? --Len B.

A: Typically the installation of a pellet stove will require the following permits:

  • The installation of the stove and flue vent requires a mechanical permit.
  • If the stove requires the installation of a new electrical circuit or the alteration of an existing circuit, an electrical permit is required.
  • If the stove has a thermostat, you'll usually also need a low-voltage permit, which is part of the electrical permit.

To obtain the permits, you'll typically need the make and model of the stove, and all the specifications for flue type, flue size and clearance to combustibles (all of that will be included in the stove's instruction sheet, or you can get it from the dealer).

Because you're-installing it in an industrial application where potentially explosive fumes may be present, there may be some additional requirements as well, so be sure to check with your local building department.

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